CN105514803A - Array micro-hollow cathode discharge-triggered gas switch - Google Patents

Abstract

The invention belongs to the technical field of pulse power, and particularly relates to an array micro-hollow cathode discharge-triggered gas switch. The switch structure mainly comprises an external insulating cylinder, main electrodes, array micro-hollow cathode discharge generators, pneumatic connectors, connecting and reinforcing parts and the like. As a trigger of the gas switch, the array micro-hollow cathode discharge generator is of an anode-medium layer-cathode structure, and a plurality of micropore arrays are perforated on the array micro-hollow cathode discharge generator by laser. The generator carries out micro-hollow cathode discharge under the action of pulsed voltage, and by utilizing a large area of high-density electrons as initial induction electrons produced by array discharge, the breakdown conduction of the gas switch is realized ultimately. Because the trigger is implemented by adopting microplasma discharge, compared with the triggering mechanism of conventional three-electrode field distortion and multi-pole multi-channel switches, the gas switch requires low triggering voltage and little energy for triggering, which is favorable for the miniaturization of switch-triggered power supplies; moreover, multi-trigger multi-point synchronous triggering can realize the multi-channel breakdown conduction of the switch and decrease the conduction inductance of the gas switch.

Description

A Gas Switch Triggered by Array Microhollow Cathode Discharge

technical field

The invention belongs to the technical field of pulse power, and in particular relates to a gas switch.

Background technique

The gas switch is a switch with gas as the insulating medium. Its main characteristics are high working voltage and strong flow capacity. It is widely used in high-power pulse power technology. It is typically used in linear transformer drivers (Linear Transformer Driver, hereinafter referred to as LTD) superior. LTD is a pulse power source that uses multiple relatively low voltage modules to obtain high-voltage and high-current nanosecond pulses through induction voltage superposition technology. Large-scale LTD is composed of tens of thousands of discharge modules. demanding. At present, three-electrode field distortion or multi-pole and multi-channel switches are mostly used in LTD devices. The basic principle of triggering is to use the trigger pulse voltage to change the electric field distribution of the switch gap to achieve overvoltage avalanche breakdown, and to change the internal electric field distribution of the switch. The amplitude of the pulse voltage is very high, which is basically in the same order of magnitude as the working voltage of the switch, making the trigger circuit of the switch itself a fast pulse power supply that is difficult to realize.

In recent years, many novel triggering methods have emerged. Ultraviolet pre-triggering and laser triggering are novel triggering methods. The triggering mechanism is different from three-electrode field distortion and multi-pole multi-channel switching. It forms high-density ionization through ultraviolet or laser irradiation switch gaps. region, to generate initial electrons and induce gap avalanche breakdown and conduction, but it also needs to be equipped with a high-energy ultraviolet or laser generator. For large-scale LTD devices, the trigger device is also very complex and bulky. Also with the aim of generating induced electrons, with the help of plasma means, gas discharge plasma is used instead of photoionization. By designing a reasonable electrode structure, high-density plasma discharge can be achieved while reducing the trigger voltage, which can help realize the miniaturization of the trigger. It will be a feasible and effective technical means.

Micro-hollow cathode (Micro-hollow Cathode, hereinafter referred to as MHC) is an electrode structure that can generate micro-discharge plasma under high pressure. Its structure is composed of an anode of any shape and a micro-hollow cathode. A certain theory (p refers to the pressure of the discharge gas component, D refers to the hollow diameter of the cathode), because the micropore size is on the order of submillimeters, it can realize glow discharge under atmospheric pressure; on the other hand, the micro-hollow cathode The ring electrode structure enables the electrons to realize the oscillation process under the action of the radial electric field of the cathode, which greatly increases the chance of impact ionization, so the discharge can achieve a high electron density; at the same time, in order to obtain a larger-scale discharge, usually in Multiple micropores are processed on a flat cathode to realize array microhole discharge; finally, due to the small size, the trigger voltage required for discharge is very low, usually only a few thousand volts. The characteristics of high-pressure discharge, large-area array discharge plasma, high electron density and low trigger voltage provide a good theoretical basis for it to be used as a trigger source for gas switches.

Contents of the invention

The purpose of the present invention is to propose a new type of gas discharge switch to solve the current traditional three-electrode field distortion and multi-pole and multi-channel gas switch. The problem of miniaturization.

The novel gas discharge switch structure proposed by the present invention is a gas discharge switch triggered by the array micro-hollow cathode discharge, specifically, the micro-plasma generated by the array micro-hollow cathode discharge has low trigger voltage and high electron density. As well as the advantages of realizing large-area porous array discharge, it is used as a trigger method in the gas switch, thereby solving the problem of high trigger voltage and difficulty in synchronous triggering of traditional three-electrode field distortion and multi-pole multi-channel gas switches. It is difficult to realize the miniaturization of the trigger power supply in terms of the application field of the scale switch.

The gas switch triggered by array micro-hollow cathode discharge provided by the present invention, the main components include: switch main electrode and its connector, outer insulating cylinder, array micro-hollow cathode discharge generator and gas circuit joint; its structure is shown in Figure 1 and Figure 2 shown, where:

The shape of the outer insulating cylinder is a hollow cylinder, and the inner wall is used to install the main electrode of the switch and the array of micro-hollow cathode discharge generators. There are a number of through holes in the middle to provide channels for triggering the electrical connection of the power supply equipment, as well as gas passages. Realize the control of the internal air pressure of the switch; the outer wall has an arc-shaped curve structure to increase the surface distance and prevent the switch from creeping;

The main electrode of the switch is two cylindrical electrodes, the upper and the lower, and there are two connecting parts for the main electrode of the switch. Each connecting part is divided into two parts: a disk and a connecting threaded rod. The lower two ends are sealed and fixed with sealing rubber rings, and at the same time, they are used as the electrical connection between the switch and the external circuit; one end of the upper and lower cylindrical electrodes is respectively connected and fixed to the center of the two discs through connecting threaded rods. 1. The other ends of the lower two cylindrical electrodes face each other to form a main electrode gap. By adjusting the depth screwed into the connecting threaded rod, the length of the main electrode gap can be flexibly changed to suit the application of different voltage requirements; see Figure 1.

Wherein, the surfaces of the ends of the two electrodes should be processed into a certain arc chamfer, so as to realize the uniform distribution of the electric field under the static voltage.

Wherein, the main electrode of the switch can be made of brass, and the connecting piece can be made of stainless steel.

The array of micro-hollow cathode discharge generators is the core component of the switch as the trigger of the switch. Its overall structure is a three-layer cylindrical structure of "anode-dielectric layer-cathode". The inner layer of the cathode is a solid cylindrical structure. The rear end is holed and tapped for electrical connection with the connector. The anode is on the outer layer, which is a hollow cylindrical structure, wrapped around the entire generator, and the dielectric layer is in the middle to isolate the two parts and achieve electrical insulation; There are a number of micro-holes realized by laser drilling on the surface of the front end of the anode. These micro-holes penetrate the anode and the dielectric layer and penetrate into the front end of the cathode to form a micro-hole array; there are three micro-hollow cathode discharge generators in the array. The ends are fixed in the middle area of the inner wall of the outer insulating cylinder, and are distributed at an angle of 120 degrees in the same plane; the rear ends of the three cathodes are drawn out of the outer insulating cylinder through the cathode lead-out electrodes, and the front surfaces of the three anodes are facing the gap between the main electrodes. The generated plasma can be accelerated to the main electrode gap on the shortest path, and the rear ends of the three anodes are connected to each other through the connecting ring, and are drawn out of the outer insulating cylinder through the extraction electrode, as shown in Figure 2. The generator realizes the micro-hollow cathode discharge under the action of the pulse voltage, and uses the large-area high-density electrons generated by the array discharge as the initial induced electrons, and finally realizes the breakdown and conduction of the switch.

The cathode and anode of the generator can be made of stainless steel, the dielectric layer is made of polytetrafluoroethylene, and all the external interfaces are chamfered to achieve a smooth transition.

The gas circuit joint adopts a quick pneumatic joint, and there are 2 gas circuit joints in total, one air inlet joint and one air outlet joint, which are fixed in the middle part of the outer insulating cylinder through threads and sealing rings, as shown in Figure 2 .

The advantages of the present invention are mainly reflected in:

1. Compared with the traditional three-electrode field distortion and multi-level multi-channel switch, triggering no longer relies on a huge amplitude pulse voltage (in the same order of magnitude as the switch operating voltage) to achieve overvoltage avalanche breakdown by changing the internal electric field distribution of the switch , but through the large-area high-density electron-induced gap breakdown generated by the micro-hollow cathode discharge of the array. Since the micro-hollow cathode discharge is a micro-plasma discharge, the required trigger voltage is very low (several kilovolts), and the required The trigger energy is very small (joule or even millijoule level), which can greatly reduce the volume and insulation strength requirements of the trigger pulse power supply, which is conducive to the miniaturization of trigger equipment for large-scale LTD devices;

2. The micro-hollow cathode structure of the array type can realize parallel and synchronous discharge of multiple microholes under the action of a set of trigger power supply equipment and one trigger pulse. On the basis of single microhole discharge, the same power supply equipment is used, but The area of the micro-discharge plasma is greatly increased, and more initial induced electrons with a larger area are promoted. The generation of large-area and high-density initial electrons can more easily induce the avalanche breakdown of the switch gap. From the perspective of switch parameters, it will help shorten the switching delay and jitter; on the other hand, due to the generation of large-area array discharge, the switch is easier. It is triggered to conduct, which allows the switch to further reduce its operating coefficient (the definition of the switching operating coefficient is: the ratio of the operating voltage of the switch to the static self-breakdown voltage of the switch), which will help improve the stability of the switching operation and reduce the switching The problem of increased self-breakdown probability caused by multiple triggers;

3. Three arrays of micro-hollow cathode discharge generators are arranged in a horizontal 120-degree distribution, which can generate three large-area array discharges in one triggering process, so that the switch can form multiple avalanche breakdown channels on the main gap and multiple arcs The channel can reduce the conduction inductance of the switch (equivalent to the parallel connection of several conduction inductances), which can achieve the effect similar to that achieved by the multi-pole multi-channel switch, but the electrode structure is simpler than the multi-pole multi-channel switch, and the trigger is easier accomplish;

4. For the traditional three-electrode field distortion or multi-pole multi-channel switch, the middle trigger electrode will serve as a transition electrode to connect the two sub-gap (the upper and lower electrodes respectively form a sub-gap with the middle trigger electrode) arc when the switch is turned on. At this time, the trigger electrode is a part of the conduction loop. Since the high voltage of the main electrode is introduced into the trigger electrode when the switch is turned on, the trigger power supply needs to fully consider electrical isolation to prevent damage by large voltage and overcurrent. However, with this switch plasma trigger mode, the trigger structure is only used as a plasma generator to generate induced electrons, which itself is not in the switch loop, and the generator itself is placed perpendicular to the switch gap, which minimizes the impact of the switch conduction loop. The impact of the trigger structure, which can simplify the design of the trigger power isolation system, is also conducive to the miniaturization of the switch trigger power supply, and further reduces the insulation requirements for the trigger electrical circuit.

Description of drawings

Fig. 1 is a schematic diagram of the main structure of the gas switch.

Fig. 2 is a top sectional view of the gas switch.

Fig. 3 is a surface structure diagram of the micro-hollow cathode of the array.

Symbols in the figure: 1-switch upper electrode connection plate, 2-electrode connection plate fixing screw, 3-sealing rubber ring, 4-switch upper electrode, 5-cathode lead-out electrode of trigger generator, 6-outer insulating cylinder, 7-switch Lower electrode, 8-switch lower electrode connection plate, 9-trigger generator anode, 10-trigger generator medium layer, 11-microhole array structure, 12-trigger generator fixing seat, 13-trigger generator cathode, 14- Trigger generator anode connection ring, 15-pneumatic connector, 16-trigger generator anode lead-out electrode, 17-anode fixing nut.

detailed description

Processing implementation of gas switch:

The main structure of the gas switch realized by the present invention is cylindrical (refer to accompanying drawing 1), and the main electrode of the switch is divided into upper and lower electrodes 4 and 7, which are distributed on the upper and lower sides of the outer insulating cylinder 6, and the outer insulating cylinder 6. In the middle of the interior is an array of micro-hollow cathode generators, as well as air inlet and outlet joints. The outer insulating cylinder is made of plexiglass. The reference dimensions are: cylinder height 90mm, cylinder wall thickness 15mm, internal and external diameters 56mm and 86mm respectively. Corresponding external dimensions can also be designed according to the specific working voltage and working environment. The anti-creepage thread on the external surface can be Correspondingly designed according to the voltage level; the main electrode of the switch is a solid cylinder with a diameter of 10 mm, made of brass material, and the edge is chamfered at 3 mm. The chamfer angle can also be designed according to the specific size of the switch through electromagnetic field simulation software to design corresponding values; The connection plate 1 of the electrode is made of stainless steel. The size of the plate is slightly smaller than that of the outer insulating cylinder. It covers the upper and lower surfaces of the outer insulating cylinder and plays the role of fixing the upper and lower main electrodes and forming an internal closed space. 2 is fixed with the outer insulating cylinder 6, and the connection plate 1 and the outer insulating cylinder 6 are sealed by the sealing rubber ring 3; the air inlet and outlet joints 15 adopt ready-made universal quick pneumatic joints, which are fixed and sealed by threads and sealing tape, and installed Convenient, can realize quick plug-in connection of gas circuit, no other sealing and fixing means are needed;

The cathode 13 and anode 9 of the array micro-hollow cathode generator are made of stainless steel, and the surface is treated with arc chamfering. The dielectric layer 10 is made of polytetrafluoroethylene, and the thickness of the anode and the dielectric layer is controlled at 0.8~1mm. The three parts are bonded It is combined and formed by means of semi-solid insulating glue for reinforcement and gap filling. The outer diameter of the generator is 8mm, and the length of the cylinder is 15mm. Distributed in the middle plane of the switch (refer to Figure 2), the cathode of each generator is drawn out through the lead-out electrode 5, and the anodes 9 of the three generators are connected through a stainless steel connecting ring 14, and the connecting ring 14 is designed as close as possible Insulate the inner wall of the cylinder and lead out through a stainless steel lead-out electrode 16. The ring-shaped wall-mounted design can minimize the influence of the trigger electrode on the electric field of the switch gap; the microhole array structure adopts laser precision machining, and the size of a single microhole 11 is 0.5~ 0.7mm, the hole spacing is 0.8~1mm, the array of microholes can refer to Figure 3, and other shapes of arrays can also be designed, the microholes penetrate the anode and the dielectric layer, and enter the depth of the front end of the cathode to a depth of 1mm, and the laser processing accuracy is high , and the consistency is better. Other reference processing methods include precision machining and etching plasma processing.

How the gas switch works:

When using this gas switch, it needs to cooperate with corresponding pulse power supply equipment, gas circuit control equipment and high voltage equipment. The upper and lower electrodes of the gas switch are connected to the external high-voltage circuit through the electrode connection plate. The external high voltage is generally a high-voltage energy storage capacitor or a charging transmission line; the quick pneumatic connector is connected to the external gas control equipment, and the gas pressure inside the gas switch can be adjusted according to the demand. and gas composition; different static self-breakdown voltages of the switch can be achieved by adjusting the distance between the upper and lower electrodes (that is, the breakdown gap of the switch), the gas composition and the gas pressure. This value determines the upper limit of the working voltage of the switch. When using, determine the appropriate value according to the actual working parameters. The determination is based on Baschen's theorem: under a certain gas composition, the product of the breakdown gap and the air pressure determines the self-breakdown voltage of the gap; the array of micro-hollow cathodes in the middle of the gas switch discharges The generator has 4 lead-out electrodes, which are the 3 cathodes and 1 common anode of the 3 generators. Generally, the 3 cathodes are connected together during implementation, and the electrical connection with the pulse power supply equipment is realized through the lead-out electrodes. When the switch is working, when a suitable trigger voltage pulse is given by the pulse power supply device, the micro-hollow cathode discharge of the array of the trigger generator can be realized, and the breakdown of the breakdown gap is induced to realize the conduction of the switch.

Claims (3)

1. a gas switch for array microhollow cathode discharge triggering, is characterized in that, comprising: switch main electrode and connector, external insulation cylinder, array microhollow cathode discharge generator and gas path joint; Wherein:

Described external insulation barrel shape is hollow shape cylinder, inwall is for installing switch main electrode and array microhollow cathode discharge generator, and centre is provided with some through holes, provides the passage of the electrical connection of triggering voltage equipment, and gas channels, realize the control of switch internal air pressure; Outer wall has circle arc curve structure to be used for increasing surface distance, prevents switch creepage;

Described switch main electrode is upper and lower two cylindrical electrodes, switch main electrode connector is two, each connector is divided into disk and connecting thread bar two parts, two disks cover insulating cylinder upper/lower terminal outside respectively, and fixing with O-ring seal sealing, simultaneously as the electrical connection of switch and external circuit; One end of upper and lower two cylindrical electrodes connects, is fixed on the centre of two disks respectively by connecting thread bar, the other end of upper and lower two cylindrical electrodes is relative, form main electrode gap, be screwed into the degree of depth of connecting thread bar by adjustment, main electrode gap length can be changed flexibly with the application of applicable different voltage request;

Described array microhollow cathode discharge generator is as the trigger of switch, for three layers of column structure of " anode-dielectric layer-negative electrode ", negative electrode, at internal layer, is solid cylinder structure, cylindrical rearward end perforate tapping, for the electrical connection with connector, anode, at skin, is hollow cylinder structure, is wrapped in whole generator outside, two parts, in centre, are isolated and realize electric insulation by dielectric layer; At the micropore that cylindrical anode leading section surface has some laser drill to realize, these micropores run through anode, dielectric layer, and are deep in cathode face, form microwell array; Array microhollow cathode discharge generator has three, and end is fixed on the central region of external insulation cylinder inwall thereafter, and in 120 degree of angular distribution in same plane; Three negative electrode rearward end are drawn outside external insulation cylinder via negative electrode extraction electrode, three anode leading section surfaces are just to main electrode gap, the plasma of generation is made to be accelerated to main electrode gap on shortest paths, three anode rearward end are interconnected by connecting ring, and draw external insulation cylinder via extraction electrode;

Described gas path joint adopts fast pneumatic joint, and this gas path joint totally 2 is 1 air inlet connections, and 1 gas outlet joint, they are fixed on external insulation cylinder middle part by screw thread and sealing ring.

2. the gas switch of array microhollow cathode discharge triggering according to claim 1, is characterized in that: the upper and lower two electrode front end faces of described switch main electrode are through circular arc chamfering process, so that the electric fields uniform distribution under realizing quiescent voltage.

3. the gas switch of array microhollow cathode discharge triggering according to claim 1 and 2, it is characterized in that: switch main electrode adopts brass material, the connector of electrode adopts stainless steel, external insulation cylinder adopts polymethyl methacrylate material, the anode of array microhollow cathode discharge generator and negative electrode adopt stainless steel, and dielectric layer adopts polytetrafluoroethylene material.